The invention relates to a drive unit for a motor vehicle, in particular a passenger car.
Drive units of this type for motor vehicles, in particular passenger cars, are already well known from the general prior art and, in particular, from series vehicle production. A drive unit of this type includes at least one internal combustion engine which has an output shaft. Via the output shaft, the internal combustion engine provides torques, for example, by way of which the motor vehicle can be driven. The internal combustion engine is configured, for example, as a reciprocating piston internal combustion engine, the output shaft being a crankshaft of the internal combustion engine.
Furthermore, the drive unit includes a starting element which can be driven by the output shaft, and a transmission which can be driven by the output shaft via the starting element. The starting element is, for example, a clutch, in particular a wet or dry clutch, or else a torque converter, in particular a hydrodynamic torque converter which can be configured, for example, as a trilock converter. The transmission can be configured, for example, as a manual transmission, in particular a manual gearbox, as an automated manual gearbox or as an automatic transmission, the automatic transmission being based, for example, on a planetary transmission. Furthermore, the transmission can be configured as a double clutch transmission, a continuously variable transmission or another transmission.
The output shaft is usually mounted on a housing of the internal combustion engine such that it can be rotated about a rotational axis relative to the housing. Bearings are provided to this end which are also denoted as main bearings in the case of the crankshaft. The main bearings are usually arranged so as to follow one another in the axial direction of the output shaft or behind one another, that main bearing which is arranged closest to the starting element in the axial direction of the output shaft usually being called the last main bearing. Higher loads of the output shaft can usually occur, in particular, in the region of the last main bearing.
It is therefore an object of the present invention to further develop a drive device of the type mentioned at the outset, in such a way that the loads which act on the output shaft can be kept particularly low.
According to the invention, said object is achieved by way of a drive unit according to embodiments of the invention.
The drive unit according to the invention is distinguished by the fact that at least one bellows is provided, via which the starting element can be driven by the output shaft. A bellows of this type is configured in the manner of a folding bellows, since it has a plurality of walls or wall regions which are arranged in a mutual overlap in the axial direction, with the result that the bellows can be pulled apart, for example in the manner of an accordion, and can be extended as a result, and thereupon can be compressed again or shortened, without the bellows being damaged or deformed plastically as a result. The concept on which the invention is based is to utilize the bellows as a balancing clutch, via which the starting element is coupled or can be coupled to the output shaft, with the result that torques can be transmitted via the bellows between the starting element and the output shaft. Loads which act on the output shaft during the operation of the internal combustion engine can be kept particularly low by way of the utilization of the bellows, in particular when an electric machine which is, for example, coaxial or is arranged coaxially with respect to the output shaft is arranged or is to be arranged between the internal combustion engine, the starting element and the transmission.
At the same time, it is possible to transmit torques which are provided by the internal combustion engine via the output shaft to the starting element, in particular its input side, via the bellows which acts as a bellow coupling, for example in a manner which is at least substantially unfiltered and is as torsionally rigid as possible, in order to drive the starting element as a result. Furthermore, it is possible by way of the use of the bellows to compensate for axial and radial movements or oblique positions of the starting element with respect to the output shaft, with the result that excessive loads of the output shaft can be avoided. This is possible, in particular, even when the starting element is at a great axial spacing from the output shaft.
In order to keep the loads which act on the output shaft particularly low and at the same time to realize a particularly effective and efficient transmission of torques between the starting element and the output shaft, it is provided in one advantageous embodiment of the invention that the bellows is formed from a metallic material. In other words, it is preferably provided that the bellows is configured as a metal bellows. The bellows is therefore configured, for example, in the manner of a folding bellows, but the bellows is not produced from rubber or an elastomer, but rather from a metallic material. The bellows then acts as a metal bellows clutch, with the result that torques can be transmitted particularly satisfactorily.
In a further refinement of the invention, a drive device which is different from the internal combustion engine is provided, by means of which drive device the starting element can be driven, in particular via the at least one bellows, and the output shaft can be driven. The drive device is, for example, a starter, by way of which the internal combustion engine can be cranked, that is to say can be started, with driving of the output shaft. In the case of the use of a drive device of this type, in particular, the spacing which runs in the axial direction of the output shaft between the output shaft and the starting element is particularly great, it being possible for projecting masses to usually occur on account of said great spacing and for an eccentricity to occur on account of any oblique position of the output shaft, in particular in the region of its last main bearing, which can lead at rotational speeds to a not inconsiderable transverse force. Said excessive transverse force and resulting, excessive loads can then also be avoided by means of the bellows in the case of the use of the drive device.
The drive device is, for example, an electric machine which can be arranged, in particular, coaxially with respect to the output shaft. Here, the respective axial directions of the output shaft and the electric machine run in the vehicle longitudinal direction. Here, for example, the electric machine is a crankshaft starter generator, by means of which the output shaft can be driven, and which can be driven by the output shaft. Furthermore, a drive device is also contemplated which permits a position of the electric machine which is axially parallel to the output shaft or crankshaft via a transverse drive as spur gear or, for example, a wraparound transmission via a belt or ladder chain. In addition to said drive device, there might also be any desired auxiliary device, for example a refrigerant compressor.
A further advantageous embodiment provides that the drive device has a first hub part which is connected fixedly and preferably rigidly to the output shaft so as to rotate with it and a second hub part which is connected to the first hub part via the at least one bellows, it being possible for the starting element to be driven by the output shaft via the hub parts and the bellows. Here, the second hub part is coupled, for example, to the starting element, in particular is connected fixedly to the starting element so as to rotate with it. The hub parts are decoupled from one another via the bellows. The result is that oblique positions can be compensated for particularly satisfactorily with a simultaneous realization of an efficient and effective transmission of torques.
The loads which act on the output shaft can be kept particularly low if the second hub part and, via said hub part, the starting element are mounted on a housing part such that they can be rotated relative to the latter in a further embodiment of the invention. The housing part is, for example, a housing of the internal combustion engine or the drive device, the second hub part and, via said hub part, the starting element and therefore the transmission being mounted and therefore supported on the housing part at least in the radial direction. As a result, loads, that is to say, in particular, forces, can be transmitted from the starting element and the second hub part to the housing part and can therefore be supported on the housing part, with the result that excessive loads of the output shaft can be avoided despite any great lever arm length with respect to the output shaft or its bearings. In other words, a mounting of the starting element and therefore the transmission is provided on the side of the transmission by way of the mounting of the starting element and the transmission on the housing part. The result is that an additional, excessive load of the output shaft and its bearings does not occur despite the use of the drive device.
In a further refinement of the invention, an adapter shaft which is configured separately from the starting element and separately from the hub parts or is provided in addition to them is provided, which adapter shaft is coupled fixedly to the starting element so as to rotate with it and fixedly to the second hub part so as to rotate with it. A simple and advantageous assembly capability of the drive unit can be provided as a result with a simultaneous realization of an effective and efficient torque transmission, it being possible at the same time for the loads which act on the output shaft to be kept particularly low. It has been shown to be particularly advantageous here if the adapter shaft and the second hub part are coupled fixedly to one another so as to rotate together in a positively locking manner, in particular via respective spline systems. For example, the adapter is coupled to the second hub part via a positively locking shaft/hub connection which is releasable, in particular is releasable without destruction.
In order to keep the installation space requirement particularly low, furthermore, the second hub part is received at least partially in the adapter shaft. As a result, it is likewise possible, for example, to keep the spacing which runs in the axial direction between the starting element and the output shaft low. The result is that a lever arm length between the starting element and the output shaft and any resulting loads which act on the output shaft can be kept particularly low.
A further advantageous embodiment provides that the first hub part is connected fixedly to the output shaft so as to rotate with it by means of at least a first screw connection, and the adapter shaft is connected fixedly to the starting element so as to rotate with it by means of at least a second screw connection, the screw connections being arranged coaxially with respect to one another. As a result, the loads which act on the output shaft can be kept particularly low with a simultaneous realization of an effective and efficient torque transmission.
In order to keep the loads which act on the output shaft particularly low, it is provided in a further embodiment that the second hub part is connected via a second bellows to an intermediate element which is different than the bellows and the hub parts and is preferably inherently rigid, which intermediate element is connected to the first hub part via the first bellows. Two bellows increase the radial and axial movement and oblique position capability of the primary hub (first hub part) with respect to the secondary hub (second hub part) without influencing the torque transmission capability.
In order to keep the installation space requirement particularly low here, it is preferably provided that at least one length region of one of the bellows is covered in the radial direction to the outside by the other bellows. In other words, it is preferably provided that the one bellows is received at least partially in the other bellows.
The starting element preferably has a flywheel or a torsional vibration damper for damping rotational non-uniformities of the output shaft and/or a clutch and/or a torque converter. Here, the torsional vibration damper can have a dual-mass flywheel. As an alternative or in addition, it is contemplated that the torsional vibration damper has torsion springs, for example bow springs, and/or centrifugal force pendulums so as to lie on the outside or inside and/or other elements for damping rotational non-uniformities of the output shaft.
It has been shown to be advantageous, furthermore, if the drive device is configured as an electric machine, in particular an electric internal rotor machine or an electric external rotor machine. The drive device is, for example, a starter generator, by means of which the internal combustion engine can be cranked, that is to say activated or started, with driving and therefore rotation of the output shaft. Furthermore, the drive device can be configured as an electric external rotor machine which has an advantageous torque capacity.
Finally, a further embodiment provides that the drive device is a transverse drive to at least one auxiliary unit which is arranged axially parallel to the output shaft, in particular the crankshaft. Here, the transverse drive can be configured, for example, as a spur gear mechanism or a wraparound transmission. In other words, the drive device can be configured as a transverse drive to one or more auxiliary units which are arranged axially parallel to the output shaft. An auxiliary unit of this type is, for example, a refrigerant compressor or an electric machine, in particular an axially parallel electric machine, or another machine.
A motor vehicle, in particular a passenger car, having a drive device according to the invention also is within the scope of the invention. Here, advantageous refinements of the drive device according to the invention are to be considered to be advantageous refinements of the motor vehicle according to the invention, and vice versa.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.
In the figures, identical or functionally identical elements are provided with identical designations.